Method of nickel plating using electrolytic nickel anodes



Sept. 26, 1944.

METHOD OF NICKEL PLATING USINGELEGTROLYTIC NICKEL ANODES' WQ L. PINNER Filed March .11, 1940 POOR CCRROS1%N BAGS NECESARY OD ROWC NO BAGS NEIEESA L5 2.0 2.5 CHLORIDE NORMALITY n 1 E I7 U r [Va/fer L. Filmer Patented Sept. 26, 1944 METHOD OF NICKEL -PLATING USING ELEC- TRQLYTIC NICKEL ANODES Walter L. Pinner, Detroit, Mich., assignor to Houdaille-Hershey Corporation, Detroit, Mich., a corporation of Michigan Application March' 11, 1940, Serial No. 323,295

3 Claims. (01. 204-49) This invention relates to a method of electrodepositing nickel using an electrolytic sheet nickel anode. More particularly, the invention relates to the electrodeposition of nickel, using electrolytic nickel sheet anodes, from a bath of nickel salts maintained under such conditions as to chloride content and pH value as to make it possible to operate the bath satisfactorily without bagging the anodes.

Anodes formed of electrolytic nickel sheets, that is, nickel electrodeposited cathodically in the form of sheets, have the advantage of being relatively cheaper per unit of weight than anodes formed from rolled or cast nickel. The matter of obtaining good anode corrosion, however, is

quite different in the case of anodes formed from electrolytic nickel sheets and anodes formed from rolled or cast nickel. It has been found, for instance, that with certain types of baths and under certain operating conditions, electrolytic nickel sheet anodes do not corrode properly, but tend to become porous and to flake off. This tendency to flake had led to the use of bags in connection with electrolytic nickel sheet anodes, since otherwise the small particles or flakes of nickel would be transferred to the surface of the work being plated, and there produce a rough, unsatisfactory plate. plating baths, especially thOSe employing a high acid concentration, or those operated under oxidizing conditions, as for instance in the presence of free chlorine or peroxide, it has notbeen practical to use ordinary cloth bags,'since they will not stand up under those conditions. Consequently, the use of electrolytic nickel sheet anodes has been comparatively restricted up to the present time.

I have now found that the obtaining of good corrosion in the case of electrolytic nickel sheet anodes is dependent upon the correlation 01' chloride content and pH value within certain rather well defined limits, and that if those limits are properly selected, it is unnecessary to employ bags for the anodes. I have further found that within the broader limits of chloride concentration and pH value, there is a more limited range of chloride concentration and pH value that should be maintained if satisfactory commercial plating is to be carried out, using electrolytic nickel sheet anodes. The more limited range of chloride concentration and pH values takes into consideration such factors as anode and cathode efiicfiencies, since if these efliciencies are too low, the plating operation could no longer be considered a commercially satisfactory one.

Furthermore, with some types of nickel It is therefore an important object of this invention to provide a method whereby electrolytic nickel sheet anodes may be employed, without the necessity of bagging, in the electrodeposition of nickel.

It is a further important object of this invention to provide a method of electrodepositing nickel, using an electrolytic sheet nickel anode, and maintaining the chloride content and pH values of the electrolyte within such limits as to obviate the: necessity of using bags with the anodes.

Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawing,

This invention (in a preferred form) is illustrated in the drawing and hereinafter more fully described.

On the drawing:

The figure represents a chart showing the chloride normality, as abscissa, plotted against pH values, as ordinates, illustrating areas within which good anode corrosion is obtained and no bags are necessary, and other areas outside of the first wherein poor anode corrosion is obtained and bags are necessary.

In determining the chloride content and pH values at which good anode corrosion was obtained, a great many nickel plating baths of varying composition were employed and operated, using electrolytic nickel sheet anodes, under ,varying conditions of temperature and current density. If, during continued operation, the anode remained smooth and free. from loose nickel particles, so that the anode could be used without being enclosed within a bag, the conditions of the plating operations were considered to be conducive of good corrosion," and it is in that sense that the term is used herein.

Among the various compositions of plating baths that were tested, were baths containing nickel chloride (NiClaBI-IzO), nickel sulfate (NiSO4.6H'2O), and boric acid (H3303). The nickel chloride content was varied from 0 to 500 g./l., and the nickel sulfate content from 0 to 200 g./1., keeping the boric acid content constant at about 40 g./l. Current densities of 40', and 200 amperes per sq. ft. were employed, based upon' the total anode area, for a'total of from 40 to 50 ampere hours.

With each of the bath compositions tested within the above range of chloride content, the pH value was varied from 0 to 4.0 or higher, and observations made as to the type of corrosion obtained on the electrolytic nickel anodes. On

the basis or the results obtained, the chart shown in the drawing was prepared.

In this chart. chloride normality is piotte along the abscissa and pH values along the ordinate. The line indicated by the reference character A represents the limiting values of chloride normality and pH below which, 800d corrosion was obtained and no bags found necessary. For chloride normalities and pH values lying above the lin A, poor corrosion was observed, such that bags would be necessary to prevent loose particles from the electrolytic nickel sheet anodes from being carried through the electrolyte to the cathode, or work undergoing plating.

It was further observed, however, that as the chloride content was decreased, especially at low pH values, the cathode efilciencies dropped very rapidly. For instance, with a temperature 01 90 F. and a chloride normality of about 0.9 and a pH of 0.7, the cathode eiiiciency dropped as low as 28%. At a temperature of 120 F., the other conditions being the same as enumerated, the

cathode eficiency was 70%.

Since such low cathode current efficiencies would render a plating bath commercially impractical, further plating tests were made to determine the range ofchloride normality and pH values within which not only good corrosion.

could he obtained but also satisfactory cathode and anode current efiiciencies. The ranges of chloride normality and pH values for the satisfactory commercial plating of nickel, using electrolytic nickel sheet anodes without bags, are represented by the area enclosed Within. the curved line B on the accompanying chart. In general, if a chloride normality and a pH value are selected which fall within the area so defined by the curved line B, a commercially satisfactory nickel plate can be obtained, using electrolytic nickel sheet anodes and nobags. This statement assumes that a suitable temperature, between the limits of 90 F. and the boiling point of the sodium chloride, potassium chloride, magnesium chloride, and the like. The "chloride normality" shown on the accompanying chart represe ts the total chloride content expressed as c oride normality. A normal chloride solution, of course, contains 35.5 grams of chloride content per liter.

As an example of a bath composition that would give good anode corrosion but would not be so electrolyte, and a suitable current density, bei tween .0 and 200 amperes per sq. ft. of cathode surfaces, will be selected, and that the nickel concentration will he sufficiently high, say above 0.75 normal nickel, to becapable or plating heavy deposits of nickel, namely deposits at least as thick as 0.0% inch.

The following will serve to illustrate an ex ample of a nickel plating bath falling within the area defined by the curved line B:

Nickel chloride (NlClafiHUl g./l 175 Nickel sulfate (NiSO46H2Q) -g./i 200 Boric acid (H1303) g./l to Current density amps/so. it I100 Temperature F 120 The chloride normality of the bath of the example Just given is approximately 1.5-N. The point indicated by the reference character X on the accompanying chart represents a bath of this chloride normality and a pH of 1.5. As indicated by the fact that the point X falls within the area defined by the curved line B, a bath of the composition given in the foregoing example is commercially operable in connection with electrolytic nickel sheet anodes without the necessity of employing bags for the anodes.

It will be understood that While in the foregoing example, the chloride normality is furnished entirelyhy nickel chloride, other sources of the chloride ion may be employed, such as commercially practicable, the following is given:

Nickel chloride g./l-- 500 Boric acid g./l- 40 Temperature F.. 110 Current density amps./sq.ft 4 pH 2.0

This point is represented by the reference character Y, which, it will be noted, lies beneath the curved line A but outside of the area defined by the line B. The chloride normality corresponding with 500 g./l. of nickel chloride is 4.25. While a bath of this composition, and operated under the conditions indicated, would not be so practical from a commercial standpoint in the plating of heavy deposits of nickel, such as nickel of a thickness of 0.001 inch and over, the bath would nevertheless give good corrosion of the anodes and eliminate the necessity of the use of bags.

As an example of a bath that would not give good corrosion, the iollowing is given:

Nickel chloride ....g./l 50 Nickel sulfate ..g./1 200 Boric acid g./l 40 Temperature F 120 Current density amps./sq. ft 40 pH 1.7

ride normalities and pH values lying within an area that defines baths having good corrosion toward electrolytic nickel sheet anodes. Once the bath has been selected, the other conditions for the operation of the bath are readily ascertainable. As stated above, in [general the temperature should be kept between 110 and 120 F. for best results, although the temperatures may be varied from as low as F. to the boiling point of the bath. Eiimilarly, a current density of around amps/so. it. will be found satisfactory for average chloride normalities in the neighborhood or 2.0, lower current densities being, in general, used with lower chloride normalities and higher current densities with higher chloride normalities. The upper limit of current density is not necessarily 200 amps/sq. ft., since current densities as high as 300 or 400 amps/sq. ft. may be employed under some circumstances.

It will also be observed from the accompanying chart that numerically lower pH values must be used with lower chloride normalities, for good corrosion, but that for a commercially practicable bath, employing chloride normalities of between about 1 and 3.5, the pH value ma be varied between about .6 and 3.1 within the area defined by the line B.

It will, of course, be understood that various details of construction may be varied through maintaining the chloride normality and pH values within the limits represented on the accompanying chart by the area beneath the line A.

2. In the method 01' electrodepositing nickel using an electrolytic sheet.nicke1 anode in an' electrolyte or a concentration equal to at least c.75-N nickel and including a chloride, the imrovement enabling the electrolytic dissolution of 20 such electrolytic nickel anodes without the separation of fine nickel particles from the anode, which comprises maintaining the chloride normality and pH values within the limits represented on the accompanying chart by the area enclosed by the curved line B.

3. In the method of electrodepositing nickel using an electrolytic sheet nickel anode in an electrolyte of a concentration equal to at least 0.75-N nickel and including a chloride, the improvement enabling the use of such electrolytic nickel anodes without bagging which comprises maintaining the chloride normality and pH values within the limits represented on the accompanying chart by the area beneath the line A while keeping the temperature 01' the electrolyte between 90 F. and its boiling point and passing an electrical current therethrouflh or from 40 to 400 amps/sq. It.

WALTER L. PINNER. 

